Irinotecan hydrochloride (CPT-11) is reportedly effective for the treatment of refractory or recurrent ovarian cancer. We investigated the antitumor efficacy and toxicity of combination therapy with CPT-11 and cisplatin in 25 patients (mean age 55 years, range 35-73 years) with refractory or recurrent ovarian cancer who had previously undergone platinum-based combination chemotherapy. Patients received two or more courses of treatment consisting of 50 or 60 mg/m2 of CPT-11 on days 1, 8 and 15 and 50 or 60 mg/m2 of cisplatin on day 1 administered intravenously. All patients were evaluable for the response and the toxicity profile. Complete responses were obtained in two (8.0%) patients and partial responses were obtained in eight (32.0%) patients, giving an overall response rate of 40% (10 of 25 patients) (95% CI 23.0-59.0%). The median duration of response was 5.5 months (range 2-27 months), the median time to tumor progression was 6 months (range 3-28 months) and the median overall survival was 12 months (range 3-39+ months). Grade 3 or 4 neutropenia, which was the most frequent and severe toxic effect, occurred in 36 (54.5%) of the 66 treatment courses and in 16 (64.0%) of 25 patients. The nadir of the leukocyte count occurred on days 18-19. Neutropenia was reversed by short-term administration of granulocyte colony-stimulating factor for 2-10 days. Less serious hematologic effects and non-hematologic effects, such as diarrhea, were also observed. This preliminary study showed that this regimen of CPT-11 and cisplatin was effective in patients with recurrent ovarian cancer.